Related Experiment Videos
Formation of active monomers from tetrameric human beta-tryptase
Ignacio Fajardo1, Gunnar Pejler
1Swedish University of Agricultural Sciences, Department of Veterinary Medical Chemistry, The Biomedical Center, Box 575, 751 23 Uppsala, Sweden.
The Biochemical Journal
|October 22, 2002
Summary
Human beta-tryptase can form active monomers after mast cell degranulation. These monomers, unlike tetramers, are inhibited by trypsin inhibitor and degrade fibronectin, suggesting a distinct biological role.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Tryptase is a mast cell serine protease stored with heparin.
- Human beta-tryptase crystallizes as a tetramer with restricted active site access.
- Mast cell activation releases tryptase and other mediators.
Purpose of the Study:
- To investigate the potential formation of active human beta-tryptase monomers.
- To characterize the enzymatic properties of tryptase monomers compared to tetramers.
Main Methods:
- Incubation of recombinant tetrameric human beta-tryptase at neutral pH and 37°C.
- Gel-filtration analysis using a heparin-containing buffer.
- Enzymatic assays measuring inhibition and substrate degradation (fibronectin).
Main Results:
- Active tryptase monomers, complexed with heparin, were formed under specific conditions (neutral pH, 37°C).
- Monomers were inhibited by bovine pancreatic trypsin inhibitor, unlike tetramers.
- Tryptase monomers degraded fibronectin, while tetramers did not.
- Monomer formation was pH-dependent and not observed at room temperature or high heparin ratios.
Conclusions:
- Human beta-tryptase can exist and remain active as monomers after mast cell degranulation and exposure to neutral tissue pH.
- Active tryptase monomers possess distinct enzymatic properties compared to tetramers, including susceptibility to inhibition and fibronectin degradation.
- These findings suggest that monomeric tryptase may contribute to the biological activities observed in allergic responses and other mast cell-mediated conditions.